The present invention relates to an ignition device and a method for controlling emergency measures for a combustion engine which has a plurality of cylinders, a separate misfiring counter being provided for each cylinder.
Ignition systems for internal combustion engines having a plurality of combustion cylinders, may have, for each cylinder, a corresponding misfiring counter in a control unit. The combustion cylinders of the internal combustion engine are ignited by ignition coils, which have a primary winding and a secondary winding, through inductive generation of a high voltage. The currents appearing in the secondary circuit may be detected by an ignition-current sensor and supplied to an ignition evaluation unit in a cylinder-selective manner. If the ignition-current sensor detects a misfiring in one of the monitored cylinders, it may emit a corresponding misfire counting signal to the evaluation unit. The evaluation unit may increase an internal misfiring counter, provided for the cylinder, by a predetermined increment value which is an adjustable, constant counter rise such as 2. If no misfiring is detected for the appertaining cylinder, the corresponding misfiring counter may be decremented by an adjustable, constant decrement value, e.g. by 1.
In the practical application of the ignition-current evaluation, it is believed that the dimensioning of the detection circuit may have A great influence. If the detection circuit is designed so that it reacts early to a misfiring, the danger may exist that ignitions in the cylinder which occurred in the desired manner are mistakenly recognized as misfirings, as well. Conversely, in a design of the detection circuit in which weaker current signals in the secondary circuit of the ignition system still generates a trigger signal in the detection circuit as well, then actually occurring misfirings produced, for example, by a carbon-fouled spark plug, may be not recognized. A certain number of occurring mal-triggerings, which occur when ignitions that are really successful are recognized as faulty, may be filtered out by first resorting to measures when the misfiring counter of the cylinder in question has reached a predefined, adjustable counter threshold value.
However, the counter threshold value may not be too high, and the counter rise, with which the counter is increased when a misfiring is detected, may not be too low, in order that a sufficiently rapid reaction in response to a plurality of misfirings occurring in succession is ensured, particularly for the protection of the catalytic converter. Since the misfiring counter in such ignition systems may have a constant counter rise, when establishing the counter threshold value, it is believed that a compromise should be found between a rapid reaction for protecting the catalytic converter when several cylinders fail simultaneously, and a statistical filtering-out in the evaluation of possibly mistakenly detected, individual misfirings at the cylinder. The counter threshold value should thus be high enough on the one hand, in order not to be exceeded by erroneous individual misfirings, and on the other hand, must be low enough to ensure a quick reaction.
It is believed that such ignition systems may have the disadvantage that they do not take into account how many misfirings have occurred in the various cylinders of the internal combustion engine, for example, in a cylinder bank. If misfirings occur simultaneously in several cylinders during one revolution, the ignition system must react particularly rapidly. In these ignition systems, the individual misfiring counters of the cylinders may be increased independently of the misfiring behavior of other cylinders. In the event of the simultaneous occurrence of misfirings in several cylinders, it is believed that this can lead to the ignition system reacting too slowly.
It is believed that the exemplary ignition device and the exemplary method for controlling emergency measures in an internal combustion engine according to the present invention, have the advantage that, when evaluating the misfiring behavior of one cylinder, the misfirings detected at the remaining cylinders are also taken into account, and a quick reaction of the ignition system is at least better ensured in the event that misfirings occur simultaneously at various cylinders.
An exemplary embodiment of the ignition device according to the present invention has a detection device for detecting the misfirings occurring at each cylinder, and a calculation device which has at least one misfiring counter for each individual cylinder, the cylinder counter, in response to a misfiring detected in the associated cylinder during one engine revolution, being increased as a function of the total number of misfirings of all cylinders detected in the preceding engine revolution.
The present exemplary embodiment and/or exemplary method of the present invention involve the fact that the misfiring counter of one cylinder may be no longer increased with a constant increment value in response to a detected misfiring as in known methods heretofore, but rather with a variable increment value which is so much the higher, the more cylinders exhibit a misfiring during the preceding engine revolution.
According to a further exemplary embodiment of the ignition device and/or exemplary method according to the present invention, when an adjustable counter threshold value is exceeded by a misfiring counter for this cylinder, the calculation device may emit an emergency-measure control signal to an emergency-measure control device for initiating an emergency measure.
According to an aspect of an exemplary embodiment of the ignition device and/or exemplary method according to the present invention, the emergency measure may be the injection of the corresponding cylinder being switched off (or interrupted).
According to a further aspect of an exemplary embodiment of the ignition device and/or exemplary method according to the present invention, the misfiring counter may be increased by a variable increment value which is calculated by multiplying the total number of misfirings in all cylinders detected in the preceding revolution, with a constant, adjustable initial increment factor.
In another exemplary embodiment of the ignition device and/or exemplary method according to the present invention, the calculation device may decrement the misfiring counter of a cylinder when the detection device detects no misfiring for this cylinder.
According to yet another exemplary embodiment of the ignition device and/or exemplary method according to the present invention, the misfiring counter may be decremented by a constant, adjustable value when no misfiring is detected by the detection device for this cylinder.
According to yet another exemplary embodiment of the ignition device according to the present invention, for each cylinder, a plurality of different misfiring counters for different emergency measures may be provided which, in each case, have separately adjustable initial increment factors and counter threshold values.
It is believed that this may provide the special advantage that various measures can be carried out at various threshold values in dependence on the values of the various misfiring counters.